This study presents a series of tests on geomaterials to investigate the mechanical behavior of unsaturated soil subjected to cyclic loading. The samples were reconstituted by using a reference material, RF Hostun sand. The speciments had saturation degree ranging between 95% and 100%. The compressibility of the pore fluid is characterized through Skempton’s parameter B depending on the sample saturation degree. After sample preparation, all the samples were subjected to cyclic loading in a triaxial dynamic testing system until reaching the zero effective stress state (or liquefaction state) to investigate the mechanical behavior including the variation of deviator stress, the development of axial strain. The results show that the value of B significantly affects the behvior of soil. When saturation degree decreases corresponding to the decrease of B value, the number of cycles needed to liquefy the sample increases. At the end of the tests, a rapid development of axial strain was observed in the saturated specimen, whereas this phenomenon did not present in the unsaturated specimen.